100 Essential Math Concepts

The math on the SAT subject tests covers a lot of ground—from arithmetic to algebra to geometry.

Don’t let yourself be intimidated. We’ve highlighted the 100 most important concepts that you’ll
need for Math 2 and listed them in this chapter.

Use this list to remind yourself of the key areas you’ll need to know. Do four concepts a day, and
you’ll be ready within a month. If a concept continually causes you trouble, circle it and come back
to it as you try to do the questions.

You’ve probably been taught most of these concepts in school already, so this list is a great way to
refresh your memory.

NUMBER PROPERTIES

1 . Number  Categories

Integers    are whole   numbers;    they    include negative    whole   numbers and zero.

A   rational    number  is  a   number  that    can be  expressed   as  a   ratio   of  two integers.   Irrational

numbers are real    numbers—they    have    locations   on  the number  line—but    they    can’t   be

expressed   precisely   as  a   fraction    or  decimal.    The most    important   irrational  numbers are 

    and π.

2 . Adding/Subtracting  Signed  Numbers

To  add a   positive    and a   negative    number, first   ignore  the signs   and find    the positive

difference  between the number  parts.  Then    attach  the sign    of  the original    number  with    the

larger  number  part.   For example,    to  add 23  and −34,    first   ignore  the minus   sign    and find    the

positive    difference  between 23  and 34—that’s   11. Then    attach  the sign    of  the number  with    the

larger  number  part—in this    case    it’s    the minus   sign    from    the −34.    So  23  +   (−34)   =   −11.